6.) 5×20=100 carti ( primul raft)
4×25=100 carti ( al doilea raft )
100+100=200 carti ( pe cele 2 rafturi)
200-100=100 carti ( ramase)
expresie :
(5×20)+(4×25)-100=
100+100-100=200-100=100
7.) 8×10 =80 bulgări
10×5=50 bulgari ( in 5 gramezi )
80-50=30 bulgari ( mai are)